Weathering test apparatus

ABSTRACT

A weathering test method comprising making active oxygen and light simultaneously act on a test piece, a weathering test method comprising successive and/or alternate steps of making active oxygen and light simultaneously act on a test piece and making at least one of light, oxygen, and water to act on the test piece, and apparatus for carrying out the methods are disclosed. In evaluating weatherability of organic materials, articles made of organic materials or articles coated with organic materials, the methods and apparatus achieve acceleration of deterioration of test pieces to greatly reduce the testing time.

This application is a Division of application Ser. No. 09/398,823 Filedon Sep. 20, 1999

FIELD OF THE INVENTION

This invention relates to a test method for evaluating weatherability ofarticles and materials thereof and an apparatus for carrying out thetest. More specifically, the invention is applied to a weatherabilitytest of organic materials, articles made of the organic materials,articles coated with the organic materials, and the like which are usedoutdoors.

BACKGROUND OF THE INVENTION

Weathering tests designed to evaluate weatherability of organicmaterials such as coatings include an outdoor exposure test in which atest piece is exposed to the weather and a traced and collected sunlightexposure test in which a test piece is exposed to traced and collectedsunlight. In addition, special test methods include an artificialaccelerated weathering test in which a test piece is irradiated withlight from an artificial light source by means of a weatheringapparatus, such as a sunshine weather meter, a UV carbon weatherometer,a xenon weatherometer, a dew panel weatherometer, and a metal halideweatherometer.

JP-A-48-60695 discloses a method for accelerating a salt spray test forevaluating anticorrosion of steel stock against seawater, in whichhydrogen peroxide-added salt water is used as testing seawater.

The above-mentioned outdoor exposure test and traced and collectedsunlight exposure test require an extremely long period of time notshorter than several months for test pieces to be deteriorated. It hasbeen impossible with these weathering tests to evaluate weatherabilityrapidly.

The problem of the artificial accelerated weathering test, on the otherhand, is that the test fails to sufficiently reproduce the deteriorationthat should have been resulted from exposure to natural weatheringconditions. That is, the deteriorated state of a test piece does notagree with that in the outdoors for the following reason. When articlesor materials are long-term exposed outdoors, their deteriorated surface,typically the coating film, shows a surface profile with fine wavinessand fine pits in a mixed state, both of which reduce the surface gloss,whereas the surface profile developed in the accelerated weathering testmainly displays fine waviness so that the reduction in gloss as observedis chiefly ascribed to the fine waviness alone.

The above-described improved salt spray test aims at acceleration of adurability test, but its application is limited to evaluation ofanticorrosion of steel stock against seawater in special fields. It doesnot apply to weatherability testing of organic materials or articlesthereof.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a test method and anapparatus for evaluating weatherability of organic materials, articlesmade of organic materials, and materials coated with organic materialsin an accelerated manner to greatly reduce the testing time.

Another object of the invention is to provide a weathering test methodand an apparatus therefor which greatly speed up deterioration of a testpiece while achieving satisfactory reproduction of outdoordeterioration.

The invention relates to a weathering test method and a weatheringapparatus for evaluating weatherability of a test piece such as anorganic material, an article made of an organic material or an articlecoated with an organic material.

The invention provides in its first aspect a weathering test methodcomprising making active oxygen and light simultaneously act on a testpiece and evaluating the resultant deterioration, and a weatheringapparatus used to carry out the test method.

The invention provides in its second aspect a weathering test methodcomprising successive and/or alternate steps of making active oxygen andlight simultaneously act on a test piece and making at least one oflight, oxygen, and water to act on the test piece, and a weatheringapparatus used to carry out the test method.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a graph showing the relationship between light exposure timeand 60° gloss in Example 2.

FIG. 2 shows the relationship between light exposure time and 60° glossin Example 3.

FIG. 3 displays the relationship between testing time and 60° gloss inExample 4.

FIG. 4 depicts the relationship between testing time and 60° gloss inComparative Example 3.

FIG. 5 shows the relationship between outdoor exposure time and 60°gloss in Comparative Example 4.

FIG. 6 is a schematic illustration of a weathering apparatus accordingto the invention.

FIG. 7 schematically illustrates another weathering apparatus accordingto the invention.

FIG. 8 is a graph of warm water immersion time and light exposure timevs. 60° gloss in Example 7.

FIG. 9 is an illustration showing the cycle of treatments in Example 8and the apparatus therefor.

FIG. 10 depicts the relationship between 60° gloss and the number oftest cycles in Example 8.

FIG. 11 shows the relationship between testing time and 60° gloss inExample 9.

FIG. 12 displays the relationship between testing time and 60° gloss inComparative Example 8.

DETAILED DESCRIPTION OF THE INVENTION

The weathering test according to the first aspect of the invention ischaracterized in that active oxygen is made to act on a test piecesimultaneously with irradiation.

Deterioration of materials is in general a phenomenon that the materialabsorbs light energy to become an active species, which reacts withoxygen in the atmosphere to undergo chemical denaturation. According tothe invention, the above-mentioned chemical reaction is accelerated bymaking light and active oxygen simultaneously act on a test piece tomarkedly speed up the deterioration phenomenon of the test piece andthereby greatly shortening the time required for testing.

In the practice of the weathering test according to the first aspect ofthe invention, active oxygen can be made to act on a test piece eitherdirectly or indirectly. The case where active oxygen is made to act onthe test piece indirectly is preferred to the case where active oxygenis made to act on the test piece directly.

For example, in a preferred embodiment, active oxygen is allowed todirectly act on a test piece by bringing active oxygen into directcontact with a test piece. This can be achieved by subjecting a testpiece to an oxygen plasma treatment.

Considering that active oxygen is difficult to handle in storing orweighing because of its high reactivity, it is another preferredembodiment that active oxygen is allowed to act indirectly on a testpiece by bringing a substance capable of releasing active oxygen(hereinafter referred to as an active oxygen-releasing substance) intocontact with a test piece. The active oxygen-releasing substanceincludes oxidizing agents containing oxygen. Oxidizing agents containingoxygen include hydrogen peroxide, ozone, peracids, peracid salts,hypohalogenous acids, and hypohalogenous acid salts. Hydrogen peroxideis preferred. The contact between the test piece and the activeoxygen-releasing substance may be either directly or indirectly. Thedirect contact can be made by, for example, coating the test piece witha liquid active oxygen-releasing substance.

However, where the oxygen-releasing substance is brought into directcontact with a test piece, it is difficult to control the action ofreleased active oxygen on the test piece, which will limit theapplicability of the test method. Therefore, it is still anotherpreferred embodiment that the active oxygen-releasing substance isbrought into indirect contact with a test piece by using a water-solubleactive oxygen-releasing substance in the form of its aqueous solution.Of the above-described active oxygen-releasing substances, water-solubleones include hydrogen peroxide and hypohalogenous acid salts. An aqueoussolution of hydrogen peroxide (hereinafter referred to as aqueoushydrogen peroxide) is particularly preferred. In this preferredembodiment using the active oxygen-releasing substance in aqueoussolution, deterioration is accelerated easily, and the concentration ofthe oxidizing agent is easily controllable, making it easy to controlthe speed of deterioration.

The contact of the aqueous solution of the active oxygen-releasingsubstance is preferably achieved by (i) immersing the test piece in theaqueous solution or (ii) dropping or spraying the aqueous solution ontothe test piece.

It is also still another preferred embodiment that the activeoxygen-releasing substance is brought into indirect contact with a testpiece by (iii) penetrating the active oxygen-releasing substance intothe test piece and letting the substance release active oxygen insidethe test piece. In this case, too, hydrogen peroxide is preferably usedas an active oxygen-releasing substance.

The water-soluble active oxygen-releasing substance includes hydrogenperoxide and hypohalogenous acid salts. Hydrogen peroxide isparticularly preferred for its high reactivity, i.e., high capability ofaccelerating deterioration. In using hydrogen peroxide in aqueoussolution, an effective concentration ranges from 0.001 to 60% by weight,preferably from 0.01 to 10% by weight. In concentrations lower than0.001%, the degree of deterioration acceleration tends to beinsubstantial for achieving the effects as expected in the invention.Concentrations exceeding 60% tend to cause deterioration too rapidly tostop the deterioration reaction under proper treating conditions, whichwill impair the accuracy of the test. With the concentration fallingwithin the preferred range of from 0.01 to 10%, reproducibility of thetest can be secured, and the test can be accomplished in a short timewith improved accuracy.

Where hydrogen peroxide is used in the form of an aqueous solution whichis brought into contact with a test piece or where hydrogen peroxide ispenetrated into a test piece, it is desirable that the test piece bekept at 0 to 120° C. At the test piece's temperature lower than 0° C.,the degree of deterioration acceleration tends to be insufficient formanifesting the effects of the invention as expected. At the testpiece's temperature higher than 120° C., cases are sometimes met with,in which some chemical reaction that would not take place outdoors mayoccur, failing to achieve the object of the test.

According to the first aspect of the invention, a test piece isirradiated with light while receiving the action of active oxygen. Lightto be used is not particularly limited as long as it has energy toactivate the material making up the test piece. Because many ofindustrially important materials mutually react with light havingwavelengths not more than 400 nm, it is desirable for the irradiatinglight to contain light rays having wavelengths of 400 nm or less. Anylight source that has been employed in conventional weathering tests canbe adopted in the present invention. Suitable light includes not onlysunlight but light from artificial light sources, such as a xenon lamp,a metal halide lamp, a carbon arc lamp, and a UV fluorescent lamp, and acombination thereof. If necessary, an appropriate optical filter can beused in combination.

The weathering test according to the first aspect of the invention ispreferably carried out by means of a weathering apparatus comprising athermostat in which a test piece is put, a means for making activeoxygen act on the test piece in the thermostat, and a means for makinglight act on the test piece. Preferred examples of the apparatus will bedescribed in detail in Examples hereinafter given.

The language “making active oxygen and light simultaneously act on atest piece” as used herein means that irradiation may not be necessarilymade to act on a test piece simultaneously with a treatment using anoxidizing agent, provided that light is made to act on the test piece inthe presence of the active oxygen.

The weathering test method according to the second aspect of theinvention comprises a first step of making active oxygen and lightsimultaneously act on a test piece and a second step of making at leastone of light, oxygen, and water to act on the test piece, the first andthe second steps being performed successively and/or alternately.

In general, outdoor deterioration of materials and articles made of thematerials (hereinafter inclusively referred to as material (s)) is aphenomenon that the material undergoes chemical denaturation by theactions of water, oxygen and light in the environment. Of these actions,the action of water is to cause hydrolysis to degrade part of thematerial to low-molecular substances and to remove the low-molecularsubstances from the surface through extraction and vaporization. As aresult, fine waviness develops on the surface of the material. When thishappens on, for example, a resin-coated article, the resin except forpigments shrinks, and fine waviness of the surface results to reduce thesurface gloss.

The action of light is to give light energy to the material to make itan active species, which reacts with oxygen in the atmosphere to formand/or sever various chemical bonds. By this action of light, part ofthe material is denatured into low-molecular substances, which areextracted and vaporized from the surface to develop fine waviness on thesurface.

Further, in the case of coating materials comprising resins and pigmentsand articles coated therewith, some pigments have photocatalysis toaccelerate local deterioration around the pigment particles. One of thecharacteristics of the surface profile observed in this case is that theresin around the pigment particles in the vicinities of the surface islost to leave fine pits on the surface. These pits as well as the finewaviness reduce the gloss of the coating film.

In fact, close examination of the surface profile of a coating filmhaving deteriorated by outdoor exposure usually reveals fine wavinessand fine pits in a mixed state. This indicates that the weatheringaction produces both fine waviness and fine pits. Therefore, in order toreproduce weathering deterioration in an accelerated manner, it isnecessary to accelerate at least one of the actions of water and oflight causing fine waviness and also the action of light causing finepits. From this viewpoint, the conventional accelerated weathering testsfail to reproduce outdoor deterioration and are inadequate as a testaiming at reproduction of outdoor deterioration.

In this regard, the weathering test according to the second aspect ofthe invention achieves acceleration and reproduction of the outdoordeterioration that could not be reproduced in the conventionalaccelerated weathering tests while properly balancing theabove-mentioned various actions. That is, the weathering test is toreproduce the surface profile of the material, for example, a coatingfilm having deteriorated by outdoor exposure.

In detail, the first step is to accelerate deterioration by making bothactive oxygen and light to act on a test piece to develop fine pits asobserved in outdoor deterioration. For example, some pigments containedin the resin coating film exert photocatalysis to induce an oxidationreaction around the pigment particles as mentioned above. It followsthat the resin is lost to leave fine pits in an accelerated manner. Inthe second step, on the other hand, fine waviness develops on thesurface of the test piece thereby achieving accelerated deterioration.Specifically, where water is made to act, the coating film, etc. arepartially hydrolyzed with water and degraded into low-molecularsubstances, which are lost through extraction or vaporization. Itfollows that the coating film, etc. shrink to develop fine waviness onthe surface thereby to accelerate deterioration. Where light is allowedto act, low-molecular substances are produced by an oxidation reactionin which light participates, and the low-molecular substances are lostdue to extraction or vaporization to produce fine waviness similarly.Where oxygen is made to act, low-molecular substances are produced by anoxidation reaction, which similarly results in fine waviness.Combination of the first and the second steps produces both fine pitsand waviness that would have developed in outdoor exposure to acceleratedeterioration, whereby outdoor deterioration can be reproduced.

The language “making active oxygen and light simultaneously act on atest piece” as used herein means that irradiation may not be necessarilymade to act on a test piece simultaneously with a treatment using anoxidizing agent, provided that light is made to act on the test piece inthe presence of the active oxygen.

The language “successive and/or alternate steps” as used herein meansthat the first step, taken as step A, and the second step, taken as stepB, can be combined in the order of A-B, B-A, A-B-A-B . . . ,A-B1-B2-A-B1-B2 . . . , and the like, wherein B1 and B2 are differenttreatments included in step B as hereinafter described in detail. Inwhat follows, the first and the second steps will sometimes be referredto as step A and step B, respectively.

Step A is a step of making active oxygen and light simultaneously act ona test piece to accelerate and reproduce the deteriorating actioncausing fine pits, which is one of the deteriorating actions in whichlight takes part. In order to make active oxygen to act, an oxidizingagent is used as an active oxygen-releasing substance. The oxidizingagent to be used is preferably selected from hydrogen peroxide, ozone,peracids, peracid salts, hypohalogenous acids, hypohalogenous acidsalts, and chlorine. Hydrogen peroxide is particularly preferred. Otherknown oxidizing agents are also employable. The oxidizing agent selectedis used in aqueous solution. The oxidizing agent can be allowed to acton a test piece by immersing the test piece in the aqueous solution ofthe oxidizing agent or dropping or spraying the aqueous solution ontothe test piece so that the aqueous solution may run thereon. Step A mayalso be effected in an embodiment wherein the oxidizing agent is made topenetrate into the test piece by the above-described manner and, afterthe aqueous solution is removed by, for example, washing with water, thetest piece is irradiated with light to make the oxidizing agent andlight act simultaneously.

Where a test piece is, for example, a coated article, the treatment withactive oxygen and light in step A results in development of fine pits onthe surface of the coating film. This deteriorated state is chieflyattributed to the oxidation reaction caused by the oxidizing agent andlight acting substantially simultaneously. Depending on the oxidizingagent selected, the oxidation reaction causes an oxygen element to bindto the test piece or causes an element other than oxygen to bind to thetest piece. In general, the oxidation occurring on organic materialsused outdoors to cause deterioration is a reaction of oxygen element'sbinding to the test piece. In order to reproduce outdoor weatheringdeterioration, an oxidation reaction in which an oxygen elementparticipates should take place.

In case where step A is undertaken by using an oxidizing agent whichinvolves an oxidation reaction in which an oxygen element participates,it is possible to cause an oxidation reaction with oxygen in step Aalone. Where such an oxidizing agent is not chosen, an oxidationreaction with oxygen does not occur in step A. In this case, however, itis possible to induce elements replacement to cause an oxidationreaction with oxygen by properly selecting the treatment to beundertaken in the following step B. In this case step B is required tocomprise a means for allowing at least oxygen to act.

Step B is to make at least one of water, oxygen, and light to act on thetest piece. Step B specifically includes the following treatments B1 toB6.

Treatment B1: immersing a test piece in warm water. The temperature ofthe warm water for the warm water immersion as used herein is from about30° C. to about 100° C.

Treatment B2: immersing a test piece in warm water while irradiating.

Treatment B3: the treatment B2 in which the warm water containsdissolved oxygen in equilibrium with an oxygen partial pressure of 0.2atm or more.

Treatment B4: irradiating a test piece in a gas containing steam.

Treatment B5: the treatment B4 in which the gas further contains 0.2 atmor more of oxygen.

Treatment B6: a treatment according to a conventional weathering testinvolving water as a load factor. The conventional weathering testuseful in treatment B6 includes an outdoor exposure test, a traced andcollected sunlight exposure test, and an artificial acceleratedweathering test using various artificial light sources.

Light to be used in steps A and B is not particularly limited as long asit has energy to activate the material making up the test piece. Becausemany of industrially important materials mutually react with lighthaving wavelengths not more than 400 nm, it is desirable for theirradiating light to contain light rays having wavelengths of 400 nm orless. Any light source that has been employed in conventional weatheringtests can be adopted. Suitable light includes not only sunlight butlight from artificial light sources, such as a xenon lamp, a metalhalide lamp, a carbon arc lamp, and a UV fluorescent lamp, and acombination thereof. If necessary, an appropriate optical filter can beused in combination.

Where step B is performed in an artificial environment, it is desirablethat the test piece be kept at 0 to 120° C. At the test piece'stemperature lower than 0° C., the degree of deterioration accelerationtends to be insufficient for manifesting the effects of the invention asexpected. At the test piece's temperature higher than 120° C., somechemical reaction that would not take place outdoors tends to occur,failing to obtain the effects as aimed.

Where the test piece is, for example, a coated article, thedeterioration accelerated in step B results in development of finewaviness on the surface of the coating film.

The above-described weathering test according to the second aspect ofthe invention is preferably carried out by means of a weatheringapparatus comprising a container in which a test piece is put, a meansfor making active oxygen and light simultaneously act on the test piece,and a means for making at least one of water, oxygen, and light act onthe test piece.

Where a test piece is irradiated with light through the wall of thecontainer in which the test piece is placed, the container should bemade of a light-transmitting material. In using light containing UVrays, a material transmitting UV rays, such as silica glass, ispreferred.

The means for making active oxygen and light simultaneously act on thetest piece includes a means for irradiating the test piece as immersedin an aqueous solution of the oxidizing agent. It is preferred for theapparatus to have a function for maintaining the temperature inside thecontainer constant so that the rate of deterioration may be adjusted. Atemperature control unit is an effective means for maintaining thetemperature inside the container constant.

The light source may be either the sun or an artificial light source. Anartificial light source is preferably incorporated into the apparatus.Any known light sources used in conventional artificial acceleratedweathering tests can be utilized, including a xenon lamp, a metal halidelamp, and a UV fluorescent lamp. To control the spectral distribution ofthe light from these light sources, it is advantageous to provide anappropriate optical filter between the light source and the test piece.

The means for making at least one of water, oxygen, and light act on thetest piece includes conventional means employed in an outdoor exposuretest, a traced and collected sunlight exposure test, and an artificialaccelerated weathering test using various artificial light sources andthe same means as used in step A for making an oxidizing agent aqueoussolution and light act on a test piece substantially simultaneouslyexcept that the oxidizing agent aqueous solution is replaced with purewater, air containing steam, and the like.

In a preferred embodiment of the apparatus, a test piece is put in acontainer made of silica glass, and the container is set in athermostat. The wall of one side of the thermostat is made of a plate ofsilica glass or of glass which also functions as an optical filter. Thetest piece is irradiated with light emitted from an artificial lightsource, such as a xenon lamp, a metal halide lamp, and a UV fluorescentlamp, through the glass plate and the wall of the silica glass-madecontainer.

The silica glass-made container has an opening at its bottom, theopening connected through piping to an external apparatus from whichliquid or gas is introduced into the container in accordance withprogrammed timing. The substance introduced into the container throughthis opening and piping includes an aqueous solution of hydrogenperoxide in step A and pure water, air at controlled temperature andhumidity, and a special mixed gas having an oxygen partial pressureincreased over that of air in step B. The test is carried outautomatically according to programmed timing.

The present invention will now be illustrated in greater detail withreference to Examples in view of Comparative Examples, but it should beunderstood that the invention is not construed as being limited thereto.In Examples and Comparative Examples, aqueous hydrogen peroxide was usedin a prescribed concentration as diluted a 30 wt % reagent of aqueoushydrogen peroxide (available from Wako Pure Chemical) with ion-exchangedwater.

EXAMPLE 1

A steel plate (7 cm×15 cm×0.8 mm) was subjected to electrodeposition,and a primer and a topcoat of white paint were applied to prepare acoated plate as a test piece. Sodium hypochlorite hexahydrate (producedby Wako Pure Chemical Industries, Ltd.), which is a liquid substance,was uniformly applied to the coated side of the plate in an amount of0.5 g/side. The plate was set to stand still in a thermostat kept at 40°C. and irradiated with light from a UV fluorescent lamp about 60 mm awayfrom the plate for 10 hours. An optical filter was placed between thecoated plate and the light source so that the light reaching the coatedplate might have wavelengths of 295 to 400 nm.

After the irradiation, the coated plate was washed with water and dried,and gloss at 60° was measured with a glossmeter GM-3D (manufactured byMurakami Color Research Laboratory). The 60° gloss of the plateimmediately after the preparation was 94, whereas that after the testwas 75.

Comparative Example 1

A plurality of coated plates prepared in the same manner as in Example 1were placed in a thermostat set at 40° C. and irradiated with UV lightin the same manner as in Example 1 for 1000 hours. Meanwhile, the coatedplates were taken out of the thermostat at appropriate time intervals,washed with water, and dried, and the 60° gloss was measured in the samemanner as in Example 1. As a result, the coated plates showed no changeof gloss from the initial value 94 until the end of the 1000-hourirradiation.

EXAMPLE 2

A plurality of coated plates (3.5 cm×15 cm×0.8 mm) were prepared in thesame manner as in Example 1. Each coated plate was put into a silicaglass-made cylindrical container (43 mm in diameter; 200 mm in height,and 2 mm in wall thickness) together with about 150 ml of 3 wt % aqueoushydrogen peroxide, and the container was closed with a silicone rubberstopper. A plurality of the thus prepared containers having the coatedplate and aqueous hydrogen peroxide therein were disposed in athermostat kept at 40° C. in such a manner that the coated side of everyplate might face a UV fluorescent lamp provided outside the thermostatabout 60 mm away from the plate. The coated side of each plate wasirradiated with light from the UV fluorescent lamp under the sameconditions as in Example 1. Meanwhile, the coated plates were taken outof the thermostat at appropriate time intervals, washed with water, anddried, and the 60° gloss was measured in the same manner as inExample 1. The initial 60° gloss immediately after the preparation ofthe test pieces was 94, whereas the 60° gloss after 100-hour irradiationwas 5. The plots of 60° gloss vs. irradiation time (light exposure time)are shown in FIG. 1.

Comparative Example 2

The same weathering test as in Example 2 was carried on a plurality ofcoated plates (3.5 cm×15 cm×0.8 mm) prepared in the same manner as inExample 1, except for replacing the 3 wt % aqueous hydrogen peroxidewith ion-exchanged water. As a result, the coated plates underwent nochange of 60° gloss from the initial value 94 until 300 hours.

EXAMPLE 3

A weathering test by irradiation was carried out in the same manner asin Example 2, except for replacing the 3 wt % aqueous hydrogen peroxidewith 1 wt % aqueous solution of sodium peroxocarbonate. The resultsobtained are plotted in FIG. 2.

EXAMPLE 4

A weathering test using a sunshine weather meter (manufactured by SugaTest Instruments Co., Ltd.) was applied to a plurality of coated platesprepared in the same manner as in Example 1. The test was undertakenunder standard conditions as specified except that highly pure water tobe sprayed to give a water load was replaced with 0.01 wt % aqueoushydrogen peroxide. The coated plate was taken out to measure the 60°gloss at given time intervals in the same manner as in Example 2. The60° gloss of the coated plate immediately after the preparation was 94,which decreased to 51 after 500 hours' testing. The plots of 60° glossvs. testing time are shown in FIG. 3.

Comparative Example 3

A plurality of coated plates prepared in the same manner as in Example 1A were subjected to a weathering test using a sunshine weather meter(manufactured by Suga Test Instruments Co., Ltd.) under standardconditions as specified. The 60° gloss of the coated plates was measuredin the same manner as in Example 4. The initial 60° gloss immediatelyafter the preparation of the coated plate was 94, which decreased to 91after 1000 hours' testing. The 60° gloss plotted against the testingtime is shown in FIG. 4.

EXAMPLE 5

A coated plate prepared in the same manner as in Example 1 was immersedin 30 wt % aqueous hydrogen peroxide (a reagent available from Wako PureChemical Industries, Ltd.) at 20° C. for 30 minutes while shielded fromlight. The coated plate was taken out of the aqueous hydrogen peroxideand immediately washed with water for 5 seconds. The washed coated platewas set in a thermostat at 40° C. and irradiated with light from a UVfluorescent lamp placed about 60 mm away from the plate for 10 hours inthe same manner as in Example 1. The 60° gloss of the coated plateimmediately after the preparation was 94, which decreased to 88 afterthe irradiation.

Comparative Example 4

A coated plate prepared in the same manner as in Example 1 was subjectedto an outdoor exposure test in Okinawa, Japan for 24 months, and the 60°gloss of the coated side was measured every 3 months. The 60° glossimmediately after the preparation of the coated plate was 94, whichdecreased to 67 after 24 months' exposure. The plots of the 60° glossagainst the exposure time are shown in FIG. 5.

Observations

Comparison between Example 1 and Comparative Example 1 reveals thatdeterioration of a coating film by light can be accelerated by directlyapplying an active oxygen-releasing substance to the coated plate,whereby reduction in gloss of the coated plate can be reproduced in ashortened period of time. Further, Examples 2 and 3 in view ofComparative Example 2 show that immersion of the test piece in anaqueous solution of an active oxygen-releasing substance achievesreproduction of reduction in gloss in a short time.

It is seen by comparing Example 4 and Comparative Example 3 thatdeterioration of the coating film of a test piece by light isaccelerated to reproduce reduction in gloss in a short time by sprayingan aqueous solution of an active oxygen-releasing substance to the testpiece. This result applies to conventional artificial acceleratedweathering tests to increase the rate of acceleration of deterioration,thereby enhancing the usefulness of the weathering tests.

Comparative Example 4 is an outdoor weathering test relying on exposureto natural weathering conditions. The time required for the coated plateto reduce its 60° gloss to 90 is 12 months in this outdoor weathering,whereas it is 8 hours in Example 2, 12 hours in Example 3, 160 hours inExample 4, and 1000 hours in Comparative Example 3. Accordingly, therate of deterioration in these Examples is 1100, 730, 55, and 8.8 times,respectively, that observed in the outdoor weathering test. From theserates of accelerated deterioration, it is understood that the weatheringtest according to the first aspect of the invention achieves remarkableacceleration of deterioration.

Apparatus Example 1

FIG. 6 illustrates an apparatus by which the first aspect of the presentinvention can be carried out easily. A test piece 15 is immersed in anaqueous solution 12 of an active oxygen-releasing substance andirradiated with UV light emitted from a light source 14 through anoptical filter and the wall of a silica glass-made container 13. Sincethe silica glass container 13 is placed in a thermostat 11, the testpiece 15 is kept at a prescribed temperature.

Apparatus Example 2

In FIG. 7 is shown another apparatus for suitably carrying out theweathering test according to the first aspect of the invention. Theapparatus comprises a casing 21, a liquid pan 22, a holding member 23which holds test pieces 25, and a light source 24. The casing 21 has afunction as a thermostat. The liquid pan 22 is put on the bottom of thecasing 21 and contains an aqueous solution of an active oxygen-releasingsubstance. The holding member 23 is positioned in the central portion ofthe casing 21 and is rotatable on a horizontal axis so that a lower partof the holding member 23 may successively be immersed in the aqueoussolution in the pan 22. The holding member 23 is a rotatable cylindricalcage, and the test pieces 25 can be attached to the inner side of thecage with their side to be tested facing the center of the rotation. Thelight source 24 is set in the casing 21 at the center of the rotation ofthe holding member 23 so as to face every test piece 25.

The holding member 23 revolves on a horizontal axis at a constant speedby means of a driving mechanism not shown. The speed of revolution isadjustable in a range of from 1 to 100 revolutions per hour. Thus, eachtest piece 25 as attached to the holding member 23 revolves in thethermostat at a given speed and, meanwhile, intermittently immersed inthe aqueous solution in the liquid pan 22 and constantly irradiated withlight from the light source 24.

Each test piece 25 is always irradiated throughout a test cycleconsisting of an immersed state in the aqueous solution, a wet statewith the aqueous solution after emerging from the liquid pan 22, a statein which water is evaporated, and the active oxygen-releasing substanceis concentrated and brought into contact with the surface of each testpiece 25 or penetrating into the inside of the test piece 25, and astate until it is again immersed in the aqueous solution. The test piece25 is repeatedly subjected to this test cycle. As a result,deterioration of each test piece 25 is accelerated efficiently.

EXAMPLE 6

A coated steel plate prepared in the same manner as in Example 1 wassubjected to an outdoor exposure test in Aichi, Japan in accordance withthe test method specified in JIS Z2381 except that 0.1 wt % aqueoushydrogen peroxide was sprayed once a day onto the coated surface of theplate under testing at noon for 10 seconds to wet the entire coatedsurface. Part of hydrogen peroxide sprayed penetrates inside the coatingfilm and acts substantially together with light. The test was started inMay and continued for 6 months. After completion of the testing, the 60°gloss of the coated plate was measured in the same manner as in Example1, and the surface profile of the coating film was observed under ascanning electron microscope (SEM) JSM-890 (manufactured by JEOL Ltd.).

The 60° gloss was 94 immediately after the preparation of the coatedplate and 75 after the 6 months' testing. The SEM observation revealedfine waviness and fine pits on the surface, which agreed with thesurface profile characteristically observed in outdoor deterioration.

Comparative Example 5

A plurality of coated plates prepared in the same manner as in Example 1were subjected to an outdoor exposure test in accordance with the testmethod specified in JIS Z2381 concurrently with Example 6. The 60° glossof the coated plate was measured at appropriate time intervals, and thesurface profile of the coating film was observed at the same time in thesame manner as in Example 6.

The 60° gloss after 6 months' exposure showed substantially no changefrom the initial value 94. Neither did the SEM observation revealed anychange. When the outdoor exposure test was further continued for anadditional 2 years and a half period (3 years in total), the 60° glosswas reduced to 80, and the surface profile showed fine waviness and finepits in a mixed state.

EXAMPLE 7

A plurality coated plates (3.5 cm×15 cm×0.8 mm) prepared in the samemanner as in Example 1 were immersed in warm water at 80° C. for 24hours and then each put into a silica glass-made cylindrical container(43 mm in diameter; 200 mm in height, and 2 mm in wall thickness)together with about 150 ml of 3 wt % aqueous hydrogen peroxide, and eachcontainer was closed with a silicone rubber stopper. The containers wereset upright in a thermostat kept at 40° C. with the coated side of eachcoated plate facing a UV fluorescent lamp which was placed about 60 mmaway from the coated surface, and irradiated with light from the lamp.An optical filter made of glass was placed between the container and thelight source so that the light reaching the coated plate might havewavelengths of 295 to 400 nm.

During the testing, the coated plates were taken out of the container atappropriate time intervals, and the 60° gloss was measured in the samemanner as in Example 1. After 50 hours' testing, the surface profile ofthe irradiated coating film was observed. The initial 60° glossimmediately after the preparation of the coated plate was 94, whereasthe 60° gloss after 50-hour irradiation was 40. The plots of 60° glossvs. irradiation time (light exposure time) are shown in FIG. 8. The SEMobservation revealed fine waviness and fine pits in a mixed state on thesurface, which agreed with the surface profile characteristicallyobserved in outdoor deterioration.

Comparative Example 6

The same weathering test as in Example 7 was carried on a plurality ofcoated plates (3.5 cm×15 cm×0.8 mm) prepared in the same manner as inExample 1, except for replacing the 3 wt % aqueous hydrogen peroxidewith ion-exchanged water. The initial 60° gloss immediately after thepreparation of the coated plate was 94, whereas that after 50-hourirradiation was 89. Under SEM observation, fine waviness was slightlyobserved but with no fine pits characteristic of outdoor deterioration.

Comparative Example 7

The same weathering test as in Example 7 was carried on a plurality ofcoated plates (3.5 cm×15 cm×0.8 mm) prepared in the same manner as inExample 1, except that the immersion in 80° C. warm water was notconducted. After 50 hours' irradiation, the 60° gloss was 58, and thesurface profile under SEM observation displayed fine pits characteristicof outdoor deterioration but no fine waviness, another characteristic ofoutdoor deterioration.

EXAMPLE 8

A coated plate (3.5 cm×15 cm×0.8 mm) prepared in the same manner as inExample 1 was subjected to 5 cycles of weathering treatments inaccordance with the diagram shown in FIG. 9. Each cycle consisted of:

treatment 1 in which the coated plate was immersed in deionized water ina thermostat set at 60° C. for 6 hours,

treatment 2 in which the coated plate taken out of the deionized waterwas put in a silica glass-made container (43 mm in diameter; 200 mm inheight, and 2 mm in wall thickness) together with about 150 ml of 0.5 wt% aqueous hydrogen peroxide, the container closed with a silicone rubberstopper and set in a thermostat at 60° C. a wall of which was made of aglass filter, and the coated side of the plate irradiated with lightfrom a UV fluorescent lamp for 3 hours through the glass filter and thewall of the silica glass-made container, and

treatment 3 in which the aqueous hydrogen peroxide was discharged fromthe silica glass container, the container was rinsed with deionizedwater, all the deionized water but about 2 ml was discharged, thecontainer was again closed with a silicone rubber stopper, and thecoated plate in the container was irradiated for 15 hours under the sameconditions as in treatment 2.

Treatment 1 corresponds to a step B, treatment 2 to step A, andtreatment 3 to another step B which is carried out in the same silicaglass container as used in treatment 2 except that the inside of thecontainer was kept in a high humidity atmosphere.

The 60° gloss of the coating film was measured in the same manner as inExample 1 at every end of one cycle. The surface profile of the coatingfilm was observed under SEM at the end of 5 cycles. The relationshipbetween 60° gloss and the number of cycles is shown in FIG. 10.

As is seen from FIG. 10, the 60° gloss, which was 94 immediately afterthe preparation of the coated plate, was reduced to 30 after 5 cycles oftreatments. The surface profile after 5 cycles revealed a mixed state offine waviness and fine pits, which was in good agreement with theconditions characteristic of outdoor deterioration.

EXAMPLE 9

A sunshine weather meter (Suga Test Instruments Co., Ltd.) was modifiedto have another spray unit in addition to the spray unit for applyinghighly pure water. A plurality of coated plates (3.5 cm×15 cm×0.8 mm)prepared in the same manner as in Example 1 were set in the modifiedsunshine weather meter and tested under the standard conditions asspecified for a standard sunshine weather meter, except that loadingwith a spray of highly pure water was preceded by loading with a10-minute spray of 0.01 wt % aqueous hydrogen peroxide from theadditional spray unit along with irradiation. The coated plates weretaken out at given time intervals to measure the 60° gloss in the samemanner as in Example 1. Further, the surface profile of the coating filmafter 500-hour testing was observed in the same manner as in Example 6.The plots of 60° gloss against the testing time are depicted in FIG. 11.

As can be seen from FIG. 11, the 60° gloss, which was initially 94,reduced to 52 after 500-hour testing. The SEM observation revealed amixed state of fine waviness and fine pits on the surface, which agreedwith the state characteristic of outdoor deterioration.

Comparative Example 8

A plurality of coated plates (3.5 cm×15 cm×0.8 mm) prepared in the samemanner as in Example 1 were tested in the same sunshine weather meter(unmodified) as used in Example 9 for 1200 hours under the standardconditions as specified. The coated plates were taken out at given timeintervals to measure the 60° gloss, and the surface profile of thecoating film after 1200-hour testing was observed in the same manner asin Example 6. The plots of 60° gloss against the testing time aredepicted in FIG. 12.

As is shown in FIG. 12, the 60° gloss, which was initially 94, reducedto 90 after 1200-hour testing. The SEM observation revealed slight finewaviness but no fine pits which are characteristic of outdoordeterioration.

EXAMPLE 10

A coated plate (3.5 cm×15 cm×0.8 mm) prepared in the same manner as inExample 1 was subjected to the same weathering test as in Example 6,except for replacing the aqueous hydrogen peroxide with a 0.25 wt %aqueous solution of chlorine. As a result, the 60° gloss, which wasinitially 94, reduced to 85 after the 6-month testing. The surfaceprofile under SEM had fine waviness and fine pits and agreed with thatobserved characteristically in outdoor deterioration.

Observations

Comparative Example 5 consists of only step B of the two essential stepsinvolved in the second aspect of the invention. Example 6 is acombination of the step B of Comparative Example 5 and step A in whichthe surface of the coated plate is wetted with aqueous hydrogenperoxide. Obviously, deterioration by outdoor exposure is accelerated inExample 6.

Comparative Example 6 is the same as in Example 7 except for replacingUV irradiation in aqueous hydrogen peroxide (step A in Example 7) withUV irradiation in pure water (corresponding to step B in Example 7).That is, Comparative Example 6 practically consists of only step B. Onthe other hand, Comparative Example 7 presents omission of the immersionin warm water from Example 7 and consists of only step A. No fine pitscharacteristic of outdoor deterioration was observed in ComparativeExample 6 (only step B), and no fine waviness also characteristic ofoutdoor deterioration was observed in Comparative Example 7 (only stepA) To the contrary, the coated plate tested in Example 7 revealed bothfine pits and fine waviness, demonstrating highly accurate reproductionof outdoor deterioration.

Example 8 shows testing equipment and procedures for efficientlyreproducing the aging of a material attending outdoor exposure byrepetition of a combination of step A and step B.

In Example 9 is demonstrated an embodiment in which an availableaccelerated weathering apparatus was slightly modified so as to servefor the weathering test according to the second aspect of the inventionthereby to produce the effects as intended. In this modified apparatus,aqueous hydrogen peroxide is sprayed to the coated plate whileirradiated to embody step A, and the situation with no spray of aqueoushydrogen peroxide-corresponds to step B. By use of the modifiedapparatus steps A and B can be performed successively and/oralternately. Compared with Comparative Example 8, it is obvious thatExample 9 achieves the effects as intended in the invention.

Example 10 displays use of an oxidizing agent causing an element otherthan oxygen to act in step A. On comparing with the results ofComparative Example 5, it is apparent that the effects as aimed in theinvention can be accomplished with such an oxidizing agent as well.

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A weathering apparatus comprising: a containerfor holding a test piece; means for simultaneously making light and anaqueous solution of an oxidizing agent act on the test piece wherein theconcentration of the oxidizing agent is a concentration of 0.01-3.0percent by weight, wherein the oxidizing agent comprises at least onemember selected from the group consisting of hydrogen peroxide,peracids, peracid salts, hypohalogenous acids, and hypohalogenous acidsalts.
 2. The weathering apparatus of claim 1, wherein said meansincludes at least one light source selected from the group consisting ofa xenon lamp, a metal halide lamp, a carbon arc lamp, an ultravioletfluorescent lamp, and sunlight.
 3. The weathering apparatus of claim 1,wherein said means includes at least one of means for immersing the testpiece in an aqueous solution of the oxidizing agent and means forspraying an aqueous solution of the oxidizing agent on the test piece.4. The weathering apparatus of claim 1, wherein: said container isequipped with a light-transmitting wall; and said means includes a meansfor making light act on the test piece, and said means for making lightact is provided outside the container.
 5. The weathering apparatus ofclaim 1, wherein said means includes means for making light act on thetest piece, and said means for making light act is provided inside thecontainer.
 6. The weathering apparatus of claim 1, wherein saidweathering apparatus comprises a casing, a liquid pan which is put inthe bottom of the casing and contains an aqueous solution of anoxidizing agent, a test piece holding member, and a light source, saidtest piece holding member being a cylinder positioned in a centralportion of the casing and being rotatable on a horizontal axis so that alower part thereof is successively immersed in the aqueous solution inthe liquid pan, and said light source being set in the casing so as toface every test piece attached to an inner side of the holding member.7. The apparatus of claim 1, wherein the apparatus holds at least onetest piece selected from the group consisting of an organic material, anarticle comprising an organic material, and an article coated with anorganic material.
 8. The apparatus of claim 1, wherein the oxidizingagent is hydrogen peroxide.
 9. The apparatus of claim 1, wherein theconcentration of the oxidizing agent is 0.01 to 1.0 wt %.
 10. Theapparatus of claim 1, wherein the concentration of the oxidizing agentis 1.0 to 3.0 wt %.
 11. The apparatus of claim 1, wherein said meansincludes a spray unit for spraying an aqueous solution of the oxidizingagent on the test piece.
 12. A weathering apparatus comprising: acontainer for holding a test piece; means for simultaneously makinglight and an aqueous solution of an oxidizing agent act on the testpiece wherein the concentration of the oxidizing agent is aconcentration of 0.01-3.0 percent by weight; and means for making atleast one of light and water act on the test piece, wherein theoxidizing agent comprises at least one member selected from the groupconsisting of hydrogen peroxide, peracids, peracid salts, hypohalogenousacids, and hypohalogenous acid salts.
 13. A weathering apparatusaccording to claim 12, wherein said means for simultaneously makinglight and an aqueous solution of an oxidizing agent act includes atleast one light source selected from the group consisting of a xenonlamp, a metal halide lamp, a carbon arc lamp, an ultraviolet fluorescentlamp, and sunlight.
 14. The weathering apparatus of claim 12, whereinsaid means for simultaneously making light and an aqueous solution of anoxidizing agent act includes at least one of means for immersing thetest piece in an aqueous solution of the oxidizing agent and means forspraying an aqueous solution of the oxidizing agent on the test piece.15. The weathering apparatus of claim 12, wherein: said container isequipped with a light-transmitting wall; and said means forsimultaneously making light and an aqueous solution of the oxidizingagent act includes a means for making light act on the test piece, andsaid means for making light act is provided outside the container. 16.The weathering apparatus of claim 12, wherein said means forsimultaneously making light and an aqueous solution of the oxidizingagent act includes a means for making light act on the test piece, andsaid means for making light act is provided inside the container. 17.The apparatus of claim 12, wherein the oxidizing agent is hydrogenperoxide.
 18. The apparatus of claim 12, wherein the concentration ofthe oxidizing agent is 0.01 to 1.0 wt %.
 19. The apparatus of claim 12,wherein the concentration of the oxidizing agent is 1.0 to 3.0 wt %. 20.The apparatus of claim 12, wherein said means for making light and anaqueous solution of an oxidizing agent act on the test piece includes aspray unit for spraying an aqueous solution of the oxidizing agent onthe test piece.